SOLUTION

Failure of the Transformer

Faults may occur in different parts and components of the transformer due to mechanical, electrical or thermal stress caused due to different conditions. Some of the most commonly occurring failures of the transformer and the causes are listed below.

 Winding failure

Windings are an important part of a transformer. In distribution side transformers there are commonly two windings. One of the primary side and the second on the secondary side.

High voltage/low current flows in the primary side winding and through electromagnetic induction voltage is stepped down and current stepped up in the secondary side winding These windings withstand dielectric, thermal, and mechanical stress during this process. The faults that occur in the winding are due to these stresses. This causes the breaking of the windings or the burn-out. 

⇒ Dielectric faults occur in the winding due to turn-to-turn insulation breakdown. These are the insulation between the turns of the winding. Insulation breakdown commonly occurs due to high current and voltage which are high above the rated values. The breakdown of the insulation results in the flashover of the winding turns and causes a short circuit. Two reasons for the high rating are

i. Lightning impulse attack with no lightning arresters

ii. Fault voltages

⇒The windings are usually of copper. Due to the copper line resistance, thermal losses occur. These thermal losses make hotspots in the winding due to bad or lack of maintenance. This overtime cause wear and tear and the decrease of the physical strength up to the point of breaking of the winding.

⇒ Mechanical faults are the distortion, loosening, or displacement of the windings. This results in the decrease of the performance of the transformer and the tearing of the turn-to-turn ratio. The main reasons that cause this fault are improper repair, bad maintenance, corrosion, manufacturing deficiencies, vibration, and mechanical movement within the transformer.